1. Field of the Invention
This invention relates to a heat exchanger for exchanging heat between air and medium flowing in an air-conditioning unit, and particularly to an automotive interior heat exchanger for heating inside air and outside air flowing in an inside/outside air two-passage unit.
2. Description of the Related Art
An inside/outside air two-passage unit has been proposed to exhibit a clouding prevention performance and a heating performance simultaneously in a compartment of a vehicle. The inside/outside air two-passage unit has first and second air passages, which are air-tightly separated from each other by an intermediate partition plane.
Inside air is sucked from the compartment into the first air passage through an inside air inlet, passes through a heat exchanger for heating, and is blown out of the first air passage into the compartment through a foot outlet. Outside air is sucked from a vehicle outside into the second air passage through an outside air inlet, passes through a heat exchanger for heating, and then is blown out of the second air passage into the compartment through a defroster outlet or a face outlet.
Inside air, which has been heated, is re-heated by the heat exchanger, and is blown from the foot outlet toward a foot portion of a passenger in the compartment. Accordingly, the heating performance in the compartment is improved. At the same time, outside air having humidity lower than that of inside air is heated by the heat exchange, and is blown from the defroster outlet toward a windshield. Accordingly, the windshield is prevented from being clouded, thereby improving the clouding prevention performance.
An interior condenser (or an interior gas cooler) 110 shown in FIGS. 5 and 6 can be used as the heat exchanger for heating described above. The interior condenser 110 is installed in a case 100 of an inside/outside air two-passage unit. The case 100 defines therein a first air passage 101 in which inside air flows and a second air passage 102 in which outside air flows. The condenser 110 has upstream side and downstream side first core portions 111, 112 for exchanging heat between refrigerant and inside air flowing in the first air passage 101, and upstream side and downstream side second core portions 113, 114 for exchanging heat between refrigerant and outside air flowing in the second air passage 102.
Refrigerant discharged from a compressor with high temperature enters the condenser 110 from an inlet side refrigerant passage 115 defined in an inlet pipe, and flows in the downstream side second core portion 114 and in the downstream side first core portion 112 in this order. Then, refrigerant flows into the upstream side first core portion 111 from the downstream side first core portion 112 through a communication pipe 116, enters the upstream side second core portion 113, and then flows out of the condenser 110 through an outlet side refrigerant passage 117 defined in an outlet pipe.
In the condenser 110, refrigerant heats inside air flowing in the first air passage 101 with room temperature (for example, 25.degree. C.) by exchanging heat when it flows in the downstream side first core portion 112 and the upstream side first core portion 111. Refrigerant further heats outside air flowing in the second air passage 102 with low temperature (for example, -20.degree. C.) by exchanging heat when it flows in the downstream side second core portion 114 and the upstream side second core portion 113.
In the condenser 110, however, heat exchange between high temperature refrigerant and low temperature outside air is performed first. After that, heat exchange between intermediate temperature refrigerant and room temperature inside air is performed. Further, refrigerant flows in a direction approximately perpendicular to outside air and inside air directions. Therefore, a temperature efficiency ratio is insufficient when refrigerant exchanges heat with inside air and outside air, so that sufficient heating performance cannot be exhibited to the compartment.